The present application relates to a memory and a data processing method that are ideal for a case where data of one bit is stored in a memory device, for example, as any one of “0” and “1”.
In related art, as information communication devices, especially, miniaturized electronic devices used particularly in mobile terminals and the like become widely used, it is desirable for devices such as memories or logic circuits configuring the electronic devices to have improved performance such as high-density integration, high operation speed, low power consumption, or the like.
In such miniaturized devices, non-volatile memories are considered to be major components used for improving the functions of the electronic devices. As the non-volatile memory, a semiconductor flash memory, a FeRAM (Ferroelectric non-volatile memory), and the like are practically implemented, and researches and developments for further improving the performance thereof are being actively undertaken.
Recently, as a new non-volatile memory using a magnetic body, for example, there is a device described in U.S. Pat. No. 5,695,864. As described above, developments of magnetic memories utilizing a tunnel magnetoresistive effect have been markedly advanced. Among such magnetic memories, memories having a configuration using magnetization inversion caused by spin transfer have attracted attention.
Here, in JP-A-2003-17782, magnetization inversion caused by spin transfer is described. The magnetic inversion caused by spin transfer is to generate magnetization inversion in a magnetic body by injecting spin-polarized electrons passing through the inside of another magnetic body into the magnetic body.
Accordingly, when the spin-polarized electrons passing through a magnetic layer (magnetization fixed layer) of which the direction of magnetization is fixed are moved into a different magnetic layer of which the direction of magnetization is not fixed, torque is applied to magnetization of the different magnetic layer. Then, by allowing a current having a predetermined threshold value or higher to flow through the different magnetic body, the direction of magnetization of the magnetic layer can be inverted.
For example, a current is allowed to flow through a magnetic tunnel junction device (MTJ device) that has a magnetization fixed layer and a magnetization free layer in a direction perpendicular to the layer faces. Accordingly, the direction of magnetization of at least a part of the magnetic layer of the device can be reversed.
Then, by changing the polarity of the current flowing through the memory device having the magnetization fixed layer and the magnetization free layer (memory layer), the direction of magnetization of the memory layer is reversed, and data is overwritten from “0” to “1” and from 1” to “0”. Hereinafter, to write data in a memory device so as to be stored therein may be abbreviated as “writing of data” or “write”. In addition, to read out data from the memory device may be abbreviated as “reading out of data” or “read-out”.
For reading out of data, stored data can be detected by selecting a memory cell by using a component such as transistor and detecting a difference in directions of magnetization of the memory layer as a difference in a voltage signal by using the tunnel magnetoresistive effect of the memory device.
In the description below, a memory device using a spin transfer is referred to as a SpRAM (Spin transfer Random Access Memory). In addition, a spin-polarized electron stream that causes the spin transfer is referred to as a spin injection current.